I've just bumped into this very useful tool for generating changelogs
from SVN commit messages:

If you update trunk/rtt, you can get the short changelog by using:
$ cd trunk/rtt
$ svn log -v -rHEAD:6017 --xml \
http://svn.mech.kuleuven.be/repos/orocos/trunk/rtt | \
tools/scripts/svn2log.py -s -O -H -p '/(branches/rtt/[^/]+|trunk/rtt)/' -u \
tools/svn-users.txt -L -o ChangeLogShort

Or the long changelog (with file names) using:

$ svn log -v -rHEAD:6017 --xml \
http://svn.mech.kuleuven.be/repos/orocos/trunk/rtt | \
tools/scripts/svn2log.py -s -O -H -p '/(branches/rtt/[^/]+|trunk/rtt)/' -u \
tools/svn-users.txt -o ChangeLog

I don't know if it is possible to use commit hooks to do this automatically
or if we ought to run it 'once in a while'. The problem is that if you update
this file, it gets a commit entry, which occurs in the changelog again,
ad infinitum. For now, I'll just bundle the generated file with the release.

Peter